Mouse is not working properly on VMWARE fusion player 12 when upgraded to bigsur

FWIW, VMWare Fusion is up to version 12.1.0. The mouse works fine with my guests. Depending on the guest, you may have to change the USB settings for the guest.

Well, I don't know what guests you are using. I think you're better off checking with VMWare Fusion support.

https://www.vmware.com/support/fusion.html